For as long as recorded history, man has recovered oil from crushed oilseeds by a variety of steps. In particular, the oil recovered from seeds such as various beans, palm oil, peanuts, etc., has formed an important portion of the food supply for people. In addition, man has long extracted oils from other types of seeds, such as linseed, flaxseed, and the like, for use in various products such as paints, medicinal products, and so forth. In most cases, the proper oilseeds are prepared by various mechanical and chemical processes so that the greatest possible amount of oil can be recovered. Generally, the oilseeds are prepared by crushing which includes rolling, grinding, or other means to reduce the seeds to a commuted form of relatively small particles. The crushed seeds are usually given a heat treatment. Then, the oil is recovered from the hot seed material by either mechanical means, such as pressing, or through the use of solvents by extraction processes, or a combination of both procedures.
Whatever the nature of the oilseeds and the oil to be recovered, it has been long appreciated that the mechanical action taken upon the seeds in the crushing operation produces finely divided solid material which contains a substantial amount of fibrous material. For example, in the conventional pressing of crushed and heated cottonseed, the oil may contain several percent of finely divided solid material. Unfortunately, this solid material also contains an appreciable portion of fibrous material. The same situation exists nearly universally in the solvent extraction processes employing a liquid solvent (e.g., hexane). In either instance, the solid material has to be removed from the recovered oil before subsequent processing.
An application of Oliver Wagner, Ser. No. 759,155, filed Jan. 13, 1977, employs a novel combination of steps in conjunction with the use of solvent recovery for oil extracted from crushed oilseeds in such a step arrangement that relatively inexpensive equipment and processing steps produce a purified oil that is substantially free of all finely divided solid material, a miscella (i.e., extracted oil plus solvent) that can be distilled to produce a pure solvent free of solids and a purified oil without requiring successive states of mechanical filtration, centrifuges, and high costs in ancillary material such as filteraid and operator time.
In accordance with said Ser. No. 759,155, there is provided a process for purifying oil removed from crushed oilseeds. The process has the steps of extracting the crushed oilseeds with a liquid dielectric solvent forming a miscella carrying finely divided solid material with a substantial content of fibrous material. The extraction consists of first contacting the crushed oil seeds with the solvent and then separating the resulting miscella from the oil seed residue. The miscella is subjected to electrofiltration by passage through a bed of dielectric particulate solids interposed within a d.c. electric field having a gradient of at least 20 kilovolts per inch whereby the finely divided solid material in substantial totality adheres to the particulate solids in the bed and provides a purified miscella that is substantially free of finely divided solid material. The purified miscella is rectified into a purified oil free of finely divided solid material and the dielectric solvent. The purified oil is passed to a subsequent utilization. The electric field in the bed of particulare solids is periodically interrupted and then, a dielectric fluid is circulated therethrough to remove the priorly adhering finely divided solid material.